The "Rust" Challenge: On the Correlations between Electronic Structure, Excited State Dynamics, and Photoelectrochemical Performance of Hematite Photoanodes for Solar Water Splitting.

In recent years, hematite's potential as a photoanode material for solar hydrogen production has ignited a renewed interest in its physical and interfacial properties, which continues to be an active field of research. Research on hematite photoanodes provides new insights on the correlations between electronic structure, transport properties, excited state dynamics, and charge transfer phenomena, and expands our knowledge on solar cell materials into correlated electron systems. This research news article presents a snapshot of selected theoretical and experimental developments linking the electronic structure to the photoelectrochemical performance, with particular focus on optoelectronic properties and charge carrier dynamics.

Identifying the bottleneck of water oxidation by ab initio analysis of in situ optical absorbance spectrum.

Hematite's (α-FeO) major limitation to efficiently splitting water using sunlight is the low rate of the oxygen evolution reaction (OER). Thus, identifying the OER rate limiting step is a cornerstone to enhancing the current under low applied potential. Different measurement techniques showed similar absorption difference spectra during a change in applied potential on the hematite anode below and above the onset of the OER in the dark and under light.

Manipulating electrochemical performance through doping beyond the solubility limit.

Improving water splitting efficiency has been the holy grail of hydrogen fuel production. Major efforts have been invested in an attempt to enhance efficiency of a common water oxidation catalyst, α-Fe2O3, through doping and alloying. Recent experiments show that higher efficiency is achieved when niobium (Nb) is added beyond the solubility limit to generate a mixture of two phases: Nb-doped and Nb-alloyed α-Fe2O3.

Hazardous Doping for Photo-Electrochemical Conversion: The Case of Nb-Doped Fe₂O₃ from First Principles.

The challenge of improving the efficiency of photo-electrochemical devices is often addressed through doping. However, this strategy could harm performance. Specifically, as demonstrated in a recent experiment, doping one of the most widely used materials for water splitting, iron (III) oxide (Fe₂O₃), with niobium (Nb) can still result in limited efficiency.